Selective catalytic reduction exhaust aftertreatment systems are an important technology for reducing harmful emissions from internal combustion engines. Selective catalytic reduction catalyst aftertreatment systems generally include a storage source for reductant (for example, diesel exhaust fluid) and a dosing unit that includes at least one of a pump unit for pressurizing the reductant. The selective catalytic reduction catalyst aftertreatment systems may also include a metering unit controlled by a control system to provide a controlled amount or rate of reductant into the exhaust stream. An injector provides a reductant solution to a decomposition region of an exhaust flow path located upstream of a selective catalytic reduction catalyst.
The control system typically requires signals from a nitrogen oxide sensor from both before and after the selective catalytic reduction catalyst. Current selective catalytic reduction catalyst aftertreatment systems use a plurality of nitrogen oxide sensors to capture data for dosing urea. For example, current aftertreatment systems may have one sensor placed before the aftertreatment component and another sensor placed behind the aftertreatment component.